Muntingia calabura fruits are rich in bioactive compounds such as antioxidants, and the consumption of these compounds is associated with cancer prevention and aging. In this study, mathematical models were used to fit the experimental data of the Muntingia calabura peel drying kinetics, and the effective diffusion coefficient, activation energy and thermodynamic properties of the process were determined. Then, the effect of the drying temperature on the antioxidant activity and phenolic compounds of fruit peels was examined using conventional extraction and ultrasonication. Among the analyzed models, the logarithmic model was selected to represent the drying phenomenon of the calabura peel kinetics. The effective diffusion coefficient decreased by 74% as the temperature increased from 40 to 60°C, and the activation energy for liquid diffusion during drying was 23.96 kJ mol-1. The enthalpy and entropy decreased with increasing temperature, while the Gibbs free energy increased by 5% for each 10°C increase in temperature. Regarding the content of phenolic compounds and the antioxidant activity of the calabura peel, it was observed that an increase in the drying temperature had a positive effect on the conservation of the bioactive compounds, making it possible to conclude that drying at 60°C and ultrasound extraction are the most suitable approach to conduct the process.

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The objective of this study was to optimize the conditions for extracting bioactive compounds from barbatimão barks. Two levels and three variables were applied to a factorial design 2 3. The independent variables were extraction temperature (30-50 °C), solution pH (7-11) and sample size (0.250-0.841 mm), while the variables the answer was the content of total polyphenols, condensed tannins and antioxidant activity. Experimental results were fitted to a first order linear polynomial model. Analysis of variance was used to determine the optimal conditions for the maximum content of total polyphenols, condensed tannins and antioxidant activity. Optimized conditions were with extraction temperature of 48 °C, pH of solution 7 and sample size of 0.841 mm. Under these conditions, the maximum values predicted were 12.76 g of gallic acid equivalent / 100 g of bark for total polyphenols, 27.91 g of catechin equivalent / 100 g of bark for condensed tannins, and 0.439 g of equivalent trolox / 100 g of bark for antioxidant activity. The extract obtained experimentally was close to the predicted values, promoting an extraction of compounds with high levels of phenolic compounds and antioxidant capacity.

Rice hydration is the main unit operation in both parboiled and germinated rice industries. Despite its importance, few studies investigate its basic principles, related to phenomena and physicochemical rice changes during hydration step in each one of these processes. Aiming to contribute to these processes, was a mass transfer kinetic study associated to identification of moisture incorporation mechanisms and alterations in the starch during the paddy rice hydration. The observed mass transfer in the process was directly influenced by the system temperature, showing changes in absorption capacity over time. A tracer pigment added to the hydration medium revealed that the mechanism of the water entrance into the grain was through diffusion through the grain coating and by capillarity through the fissures. The thermal analysis and scanning electron micrographs (SEM) showed that hydration at 55 and 65 C presented partial and total gelatinization of the starch, respectively. The models addressed allowed describing the moisture gain for various thermal conditions. The generalized model obtained was able to predict the experimental moisture at any process time for any of the investigated temperatures with a 5% maximum deviation. This research contributes significantly to the understanding of the phenomena involved in rice hydration, aiding in the development of operational parameters; they also point to a mathematical model that is able to represent the experimental data in a manner that is simple, quick, and inexpensive, particularly for industrial use.Practical Applications: This study presents a paramount contribution to the timetemperature binomial establishment in the rice hydration process, since it provides as a process tool, the kinetic hydration model of moisture incorporation, as well as reveals the alterations in the grain microstructure. The discoveries can boost industries that process paddy rice, especially those located in poorer areas that lack knowledge and information, helping to improve operating conditions. Such a context justifies the investigation of models that may be easily applied, perform well, and are inexpensive, such as is the model presented in the present work, which may be applied by industries to monitor and also specify optimal operation conditions.